Hide taskbar when launcher receives nav and keyguard showing

* On large screen we receive notification shade expanded
signals even on keyguard.
* Add a check to not show taskbar if keyguard is showing

Fixes: 223465924
Test: Taskbar doesn't show on 3 button nav except
on bouncer, as expected.

Change-Id: I4a7ea14422eda13ae8571793ed7ba1a1964072d6